Double-acting drop hammer



Oct. 29, 1940.

R. P. FITZGERALD DOUBLE-ACTING DROP HAMMER Filed Oct. 11, 1939 5 Sheets-Sheet 2 lnven'ror.

Reginald F? Fifggerold b WMW A'fly s.

Oct. 29, 1940. R, P. FITZGERALD DDUBLE-ACTING DROP HAMMER v 5 Sheets-Sheet 3 Filed Oct. 11, 1939 Fig. 4:.

Fig. 5.

I-nvenTon Reginald P. FiTggerold ylfieow MM ATTYS.

Oct. 29, 1940.

R. P. FITZGERALD DOUBLE-ACTING DROP HAMMER Filed Oct. 11, 1939 5 Sheets-Sheet 4 w? mwww. e n P MM R. P. FITZGERALD DOUBLE-ACTING DROP HAMMER Filed Oct. 11, 1939 5 Sheets-Sheet 5 lnven'ror. Reginald F? FiTggerold byw lfm.

Patented Oct. 29, 1940 UNITED STATES PATENT OFFICE DOUBLE-ACTING DROP HAIVHVIER.

Application October'll, 1939, Serial No. 298,902

17 Claims.

This invention relates to improvements in' power operated hammers having a movable hammer and a cooperating movable anvil subject respectively to separate forces tending to propel the hammer and anvil toward each other, with means actuated by fluid under pressure to separate said hammer and anvil and operable upon release of such pressure to permit said separate forces to propel the hammer and anvil toward each other.

More particularlythe invention relates to improvements in drop hammers of the type disclosed in my prior Patent No. 1,990,478, granted February 12, 1935.

One of the objects of the invention is to provide a simplified construction for controlling the supply and release of fluid under pressure from the respective means which separate the hammer and anvil.

In the construction .disclosed in my prior patent a lifting cylinder is provided with a piston connected to the anvil and operated by said fluid under pressure to lift the hammer. The anvil is supported upon the rod of the piston of a cylinder which is mounted in the base of the machine, and fluid under pressure introduced into the lower chamber of the cylinder tends to propel the anvil upwardly and to impart to it a momentum equal to that of the dropping hanmier at the moment of impact. Fluid under the same pressure introduced into the upper chamber of the cylinder from the same source serves to depress the anvil against the force of fluid under pressure in the lower chamber of the cylinder by reason of the weight of the anvil in addition to the pressure introduced into the upper chamber of the cylinder.

In that construction connected operating valves in the conduits'leading to the hammer cylinder and to the upper chamber of the anvil cylinder 40 permit simultaneous introduction of air under pressure. When the hammer and anvil have thus been separated by the fluid under pressure,

the operating valves are rotated to open position. The exhaust conduits from the hammer 45 cylinder and from the upper chamber of the anvil cylinder are, in the construction disclosed in my previous patent, unconnected, but are provided with means normally maintaining the exhaust valves in closed position. Manually operable means are provided for rotating the exhaust valve for the hammer cylinder toward open position to control the dropping of the hammer, and fluid operated means are provided for simultaneously actuating the exhaust valve or the upper chamber of the anvil cylinder to open position in correlation to the opening of the valve in the exhaust conduit of the hammer cylinder.

One ofthe objects of the present invention is to provide physically connected exhaust valves for the hammer cylinder and the upper chamber 6 of the anvil cylinder normally maintained in closed position and movable simultaneously to position to correlate properly the rate of escape of fluid under pressure from said exhaust conduits, the exhaust valve for the lower conduit 10 being of predetermined greater capacity than that of the exhaust valve for the hammer cylinder.

An important feature of the present invention consists in the introduction in the exhaust branch 15 of the conduit leading from the upper chamber of the anvil cylinder of a normally closed supplemental valve and providing means for rotating the same to open position when the hammer has dropped a predetermined portion of its stroke, in combination with an exhaust valve complementary to the exhaust valve for the anvil cylinder but of a larger diameter than the exhaust valve for the, anvil cylinder, the exhaust valves for the hammer and anvil cylinder having ports of similar contour provided with tapering walls and so coordinated as properly to correlate the rate of escape of fluid under pressure from the respective cylinders that the anvil will acquire the same momentum as that of the hammer at the point 30 of impact while traveling through a relatively short distance as compared to the distance traversed by the hammer. Desirably the exhaust valves for the hammer cylinder and for the anvil cylinder are directly connected to a rod which is manually controlled preferably by pedal mechanism, as hereinafter described, thereby enabling the use of a simplified controlling mechanism which will enable the operator at all times to control the force of the blow upon the material being fashioned.

A preferred embodiment of the invention is illustrated in the accompanying drawings, in which,

Fig. 1 is a front elevation of a drop hammer of the character above described;

Fig. 2 is a side elevation of the same, the foundation and support for the power hammer being omitted;

Fig; 3 is a horizontal sectional view on line 3-3 Fig. 2, showing portions of the flexible connection between the operating pedal and the rod which connects the exhaust valves for the hammer and the anvil cylinders;

Fig. 4 is a detail plan view of the cylinder- 5 supporting beam and hammer cylinder support showing the hammer cylinder in horizontal section and also broken away and illustrating the inlet and outlet conduits for said cylinder in section;

Fig. 5 is a similar plan view of the integral base and valve block, portions thereof being broken away to illustrate .the inlet and exhaust conduits in horizontal section and also showing the I piston rod for the anvil in horizontal section;

Fig. 6 is a comparative view of the exhaust valves for the hammer and anvil in concentric arrangement to illustrate particularly the relative areas and identity of construction of the valve ports;

Fig. 7 is a diagrammatic view of the hammer illustrating graphically the conduits and valves and actuating mechanism for operating the hammer when the hammer is at rest, the valves being shown in a position to admit fluid under pressure to the hammer cylinder and to the upper chamber of the anvil cylinder when fluid under pressure is supplied thereby to raise the hammer and depress the anvil;

Fig. 8 is a diagrammatic view illustrating in the upper part of the figure the position of the operating and exhaust valves for the hammer cylinder after the hammer has been raised, and in the lower part of said figure the corresponding position of the operating and exhaust valves for the anvil cylinder and also the position of the intermediate supplemental valve after the anvil has been depressed, showing the manner in which fluid under pressure is supplied to the hammer and anvil cylinders respectively to hold the hammer up and the anvil in depressed position prior to the rotation of the exhaust valves to exhaust position to permit the initial dropping movement of the hammer;

Fig. 9 is a view similar to Fig. 8 showing the relative position of the operating and exhaust valves for the hammer cylinder and the valves controlling the exhaust conduit for the anvil cylinder when the exhaust valves for the hammer and anvil cylinder have been rotated to exhaust position, the supplemental valve remaining in closed position during the initial dropping of the hammer;

Fig. 10 is a similar view showing the position of said valves with the supplemental valve rotated to exhaust position when the hammer is dropped a predetermined portion of its stroke;

Fig. 11 is a similar view showing the position of said valves when automatically positioned Just before the hammer and anvil meet and in position to permit the lifting of the hammer and depressing the anvil;

Fig. 12 is a similar view showing the relative positions of the operating, exhaust and supplemental valves when the hammer is again raised and the anvil depressed and just prior to the rotation of the exhaust valves to the open position illustrated in Fig. '7;

Fig. 13 is a detail view, mainly in vertical section, of the exhaust valve mechanism for the anvil cylinder, the valve being shown mainly in elevation; and,

Fig. 14 is a horizontal sectional view of the same on line l4-I4 Fig. 13.

As illustrated in the accompanying drawings (Figs. 1 and 5), the drop hammer construction is mounted upon a suitable concrete foundation I having a central well 2 and a suitable recess 3 presenting a horizontal platform 4 upon which are bolted parallel girders 5 which support the base of the drop hammer. The base of'the drop hammer desirably is an integral rectangular construction 6 having a flat base I, a flat top 8 connected centrally by an integral substantially cylindrical member 9 from which an integral web l0 extends longitudinally of one end and merges into a vertical end wall connecting the top and bottom plates. Other vertical webs II extend from the central member 9 at right angles to the web I0 and integrally connect the top and bottom. Another integral web I2 of greater thickness extends from the central member 9 lengthwise of the base and is provided with conduits for the admission of fluid under pressure to the anvil cylinder and the release of pressure therefrom and also provides a valve block in which valves controlling the inlet and exhaust ports are mounted. The web I2 extends to and is integrally connected to vertical end wall connecting the top and bottom of the base.

The central cylindrical portion 9 is provided with a vertical bore which forms a bearing for the piston rod l3 of the anvil cylinder. The anvil cylinder I4 is provided with a peripheral flange which is bolted or welded firmly to the bottom plate of the base and is in axial alinement with the piston rod I3 and a piston head I5, which is fixedly secured upon the piston rod I3, is reciprocably mounted in the cylinder I4.

The cylinder I4 is provided with a bottom flange I6 to which is bolted or otherwise secured a complementary flange at the upper end of a preferably cylindrical reservoir I! which extends into the well 2 and forms a lower chamber of the cylinder I4. Fluid, preferably under constant pressure, is introduced into this lower chamber of the cylinder through a pipe IS. The web I2 of the base is provided with a suitable conduit I9 which leads to the upper chamber of the cylinder I4 above the piston I5. Fluid under pressure is supplied to the conduit III through a main inlet branch 20 and a supplemental inlet branch 2I. The conduit I9 is also provided with an exhaust branch 22 which leads in a substantially straight line from the conduit I! to the atmosphere or to a suitable muflier.

Suitable valves are provided in the valve block I2 for controlling introduction of fluid under pressure into the upper chamber of the cylinder and the exhaust of said fluid under pressure therefrom as will hereinafter more fully appear. I

One of the novel features of the present ine vention consists in providing a valve-controlled exhaust conduit which is substantially straight, thereby reducing to a minimum uncontrolled resistance to the escape of fluid under pressure from the anvil cylinder when the controlling valves for the fluid under pressure are rotated to open position.

The superstructureof the drop hammer, which is mounted upon the base, comprises a pair of vertical parallel columns 23 and 24 which are bolted, welded or otherwise secured to the top I of the base and are connected at their upper ends by a horizontal yoke or cylinder-supporting beam 25 which is suitably bolted to the upper ends of'the columns. The cylinder-supporting beam 25 is provided with a central preferably rectangular boss upon which is bolted a complementary rectangular base of a cylindrical sleeve 28 which is provided withinternal screw threads adapted to receive a'screw threaded lower end of the lifting cylinder 21 for the hammer. The upper end of the hammer cylinder 21 is provided with a cap 28 which is rigidly secured to bosses on the sleeve by tension rods 29 thereby providinga rigid construction which will .avoid the likelihood of loosening of the cylinder, The cylinder-supporting beam 25 is also provided with a downwardly extending cylindrical boss 30 forming the cylinder of a dash pot for cushioning the upward movement of the hammer and which may be of a somewhat similar construciton to that disclosed in my Patent No. 1,990,478 aforesaid.

, A suitable piston which is reciprocably mounted in the hammer lifting cylinder 21 is provided with a vertical piston rod 3| which extends axially through the dash pot 30 and is connected at its lower end to the head 32 of a hammer. The lower portions of the vertical columns 32 and 24 desirably are of hollow rectangular form while the upper major portions of said columns are fashioned to provide guideways 33 for complementary guides upon the sides of the hammer. The lower end of the hammer is provided with a suitable, preferably dovetail, recess 34 to receive a complementary projection upon a suitable hammer die 35. The anvil 36 is mounted upon the upper end of the piston rod 13 and is provided with laterally extending guides 31 which engage suitable vertical guideways 38 in the lower portions 23 and 24 of the respective vertical columns. By reason of the construction above described therefore introduction of fluid under pressure into the hammer lifting cylinder 27 below the piston thereof will raise the hammer and the exhaust of fluid under pressure therefrom will permit the hammer to drop as in usual drop hammer constructions. Fluid under pressure, which is admitted into the reservoir II which communicates with and preferably is a part of the lower chamber of the anvil cylinder l4, exerts a constant force tending to project the anvil upwardly, while fluid under pressure introduced into the upper chamber of the anvil cylinder through the conduit l9 tends to force the piston of the anvil cylinder downwardly. Desirably fluid under pressure from the same source is introduced into both the upper and lower chambers of the anvil cylinder and the weight therefore of the anvil, the piston rod to which it is connected and the piston is suflicient to depress the anvil against the pressure in the lower chamber of the anvil cylinder until the anvil comes to rest at a predetermined level. Upon release of pressure in the upper chamber of the anvil cylinder, the constant force of the fluid pressure in the lower chamber will project the anvil upwardly and valve mechanism is provided which will so coordinate the force thus produced upon the anvil to the momentum of the dropping hammer that the momentum of the anvil will equal that of the dropping hammer at a predetermined position of impact, so that the hammer and anvil will meet within a predetermined regulatable zone with substantially equal momentum, thereby causing the. force of each to be absorbed by the other and preventing transmission of vibration to the frame of the machine as in the construction disclosed in my prior Patent No. 1,990,478.

In the present construction the exhaust branch of the conduit from the anvil cylinder is provided with an exhaust valve of greater capacity than that which controls the exhaust from the anvil cylinder, and is also provided with a supplemental valve which is automatically operated when the hammer is dropped a predetermined distance to cause the anvil to acquire a momentum equal trolled pneumatically actuated means for rotating the operating valves to exhaust position which permitted the hammer to drop and by the automatic rotation of the exhaust valve to open position after the hammer dropped a predetermined distance. In that construction the rate of exhaust of fluid under pressure from the hammer cylinder was regulated by an adjustable rotary restricting valve provided with an angular port and the rate of exhaust of fluid under pressure from the anvil cylinder was regulated by a vertical reciprocable valve having an angular port and which was positioned by mechanism actuated by the pressure of the fluid in the exhaust conduit leading from the hammer cylinder.

One of the objects of the invention, as heretofore stated, is to simplify the mechanism for controlling the action of the hammer. This is accomplished by controlling the release of air under pressure from the hammer and anvil cylinders by physically connected exhaust valves having coordinated ports provided with tapering walls and adapted to be so adjusted as not only to release fluid under pressure from the hammer to permit the hammer to drop, but to enable such manual adjustment of the connected valves as to enable the operator to control the hammer and anvil during every moment of their respective movements, so that the operator is able at all times to control the force of each blow. By the present construction a very considerable portion of the mechanism for controlling the action of the hammer and anvil as disclosed in my prior patent has been eliminated, and a simplified construction provided which permits a much more efficient and flexible control of the hammer and anvil mechanism than that disclosed in my prior patent.

The mechanism for supplying air under pressure to the hammer cylinder and to the upper chamber of the anvil cylinder comprises a main supply pipe 39 which leads from a source of fluid under pressure, such as compressed air, and which communicates on the one hand with a pipe 40 which leads to the inletbranch 4| of a conduit 42'which communicates with the hammer cylinder. The pipe 40 is provided with a manually operable valve 43 by which the supply of air under pressure can be cut off or admitted to the pipe 40, (see Figs. 7 and 4). .The pipe 39 also communicates with a pipe l8 (Fig. 1) which leads to the reservoir I! which forms part of the lower chamber of the anvil cylinder. The pipe I8 also communicates with a branch pipe 44 which communicates with the inlet branch (Fig. 5) which leads to the conduit l9 which communicates with the upper chamber of the anvil cylinder. A manually operable valve '45 in the pipe [8 (which may be an extension of the pipe 39) provides means for cutting off or admitting air under pressure to the pipes l9 and 44, The admission and exhaust of air under pressure from the conduit 42 of the hammer cylinder and of the conduit IQ of the anvil cylinder are controlled by suitable connected operating valves and connected exhaust valves, there being an automatically operable supplemental valve in the exhaust branch 22 of the conduit l9 which communicates with the anvil cylinder. The operating valves for the conduits 42 of the hammer cylinder and I9 of the anvil cylinder may be and desirably are of the construction disclosed in my prior Patent No. 1,990,478, and which are provided with ball bearings as disclosed therein. The valve 46 for controlling the admission and escape of fluid from the hammer cylinder is located at the junction of the conduit 42 which leads from the hammer cylinder with the inlet branch 4| and the exhaust branch 41 as shown in Fig. 4, and is provided with diametrically opposite ports for establishing communication between the conduit 42 and exhaust branch 41 'and a port 46a: at right angles thereto for establishing communication between the inlet branch 4I and the conduit 42.

The operating valve 48 for admitting fluid under pressure to the upper chamber of the anvil cylinder and the exhaust of fluid under pressure therefrom is of similar construction and is located at the junction of the conduit IS with the inlet conduit 20 and the exhaust conduit 22 as illustrated in Fig. 5. This valve is also provided with diametrically opposite ports for establishing communication with the exhaust conduit and with a port 48:: at right angles thereto for establishing communication between the inlet conduit 20 and the conduit IS.

The operating valves 46 and 48 are connected by a vertical rod 49 which has secured to it cams 60 and BI having spirals adapted to be engaged ondary blow and thereupon to continue the separation of the hammer and anvil. The cam which is adjustably secured to the rod 46 at a predetermined position near the predetermined upward limit of movement of the hammer, is operated by the hammer in its upward movement to rotate the operating valves to exhaust position. Both the operating valves are therefore automatically positioned by the hammer during its dropping and lifting movements instead of being manually controlled as in my prior patent aforesaid.

The exhaust valve 62 for the hammer cylinder is located in the exhaust branch 41 of the conduit 42 and is provided with diametrically opposite ports 53 to establish direct communication through the exhaust branch 41 with the. atmosphere, or with a suitable mumerr The valve 62 is also provided with a relatively small port 64 adapted to establish communication with the exhaust branch 41 when the exhaust valve is rotated to closed position at which time one of the ports 53 will register with a duct 66 leading to the inlet branch 4|, the purpose of this construction being to enable fluid under pressure to pass from the source through the duct 66 and exhaust valve 62 into the exhaust branch 41, thence is flxedly secured to the upper end of an oper'ating rod 66 the lower end of which is coupled to the stem 61 of an exhaust valve 66 which controls the release of fluid under pressure from the upper chamber of the anvil cylinder. The exhaust valves for the hammer cylinder and for the anvil cylinder are thus physically connected and simultaneously rotatable by manually controlled mechanism in such manner that the operator can control their operation at all times, thereby enabling him to cause the hammer and anvil to strike any desired blow upon the material being fashioned.

The exhaust valve construction for the anvil cylinder is illustrated in detail in Fig. 13 and comprises a cylindrical sleeve 68 which is fitted within a corresponding vertical bore in the web I! of the base 6 through which the exhaust branch conduit 22 extends. The sleeve 69 is provided with diametrically opposite openings which are preferably of the same size and register with the exhaust branch 22. The exhaust valve 68 is in the form of a hollow cylinder which is closed at its lower end by a head 60 which is provided with a downwardly extending gudgeon 6i and is secured to the cylinder by welding 62 uniting the periphery of the head with the cylinder wall. An annular ball bearing 63 is located between the gudgeon 6| and the sleeve 69 and is securely held in place and the lower end of the sleeve effectively closed by a cap 64 which is screwed'in the web or valve block l2 of the base and has a flange underlying the lower end of the sleeve and the outer race of the ball bearing. The upper head 65 of the cylindrical valve is similarly secured in the upper end of the cylinder by welding 66 and is provided with an upwardly extending'gudgeon 61 which is integral with the valve stem 51. A ball bearing 68 fits between the gudgeon 61 and the sleeve 59 and is secured in place by a cap 69 which is screwed into the upper end of the web or valve block I! and abuts and overlies the upper end of the sleeve and ball bearing 68. The cap 69 is provided with a central recess to receive a packing l0 fitting around the valve stem .51 and the packing is held in place by a disk Ii fltted in a counterbore in the cap and a spring ring 12 mounted in a groove beneath the disk '|l. By reason of the construction described all leakage of air under pressure is avoided.

One of the principal features of the invention relates to the construction of the'exhaust valves for the hammer cylinder and for the upper chamber of the anvil cylinder and the correlation thereof in such a manner as to enable the movement of the hammer and anvil to be controlled by the operator at all times. In the present construction, as in that disclosed in my prior patent aforesaid, means are provided for delaying the exhaust of fluid under pressure from the anvil cylinder until the hammer is dropped a predetermined distance, but in the present construction diflerent supplemental valve mechanism is provided for this purpose.

In order to permit the more rapid exhaust of fluid under pressure from the upper chamber of the anvil cylinder than from the hammer cylinder when released after the hammer is dropped a predetermined distance, the exhaust valve for the upper chamber of the anvil cylinder is of larger diameter and is provided with a port of greater area than that of the exhaust valve for drawings in which the cylindrical exhaust valve 58 for the anvil cylinder is shown concentrically surrounding the cylindrical exhaust valve 52 for the hammerv cylinder. It will, of course, be understood that this figure of the drawings is merely for the purpose of comparison and does not illustrate any assembled construction.

In order to control the rate of exhaust of fluid unde the upper chamber of the anvil cylinder, the exhaust valves 52 and 58 are provided with outlet ports, preferably of identical contour, which as illustrated comprise diametrically opposite vertical elliptical openings 18 and 14 in the respective valves, one side wall of each port merging into preferably curved tapering extensions I5 and 16 in the respective valves, as illustrated particularly in the comparative Fig. 6, from which it will be obvious that the port in the exhaust valve for the anvil cylinder is of the same contour in all respects, but of larger area than the port of the exhaust valve for the hammer cylinder. By thus properly correlating the contour and areas of these ports simultaneous rotatable movement of the exhaust valves will properly coordinate the escape of fluid under pressure from the hammer cylinder and anvil cylinder throughout any rotative adjustment of the valves, thereby enabling the operator at all times to control the force of the blow.

The present invention also includes novel mechanism for delaying the release of fluid under pressure from the upper chamber of the anvil cylinder until the hammer is dropped a predetermined distance. In the construction disclosed herein a supplemental controlling valve 11 is mounted in a suitable sleeve 'l8 in the exhaust branch 22 of the conduit l9 leading from the upper chamber of the anvil cylinder and desirably is constructed with ball bearings of the character above described. Thisvalve desirably is constructed in the same manner as the operating and exhaust valves above described and isprovided with diametrically opposite ports 19 adapted to establish a direct passage through the branch conduit 22. It is also provided with a relatively small port 88 at right angles to the ports 19 adapted when placed in communication with the inlet conduit 2| to establish communication through one of the ports 19 with the section of the exhaust branch 22 which communicates with the operating valve 48.

By reason of this construction fluid under pressure may be introduced from the source through the pipe 44, conduit 2|, a portion of the exhaust branch 22, and the operating valve 48 when in exhaust position to the upper chamber of the anvil cylinder, thereby to continue the full fluid pressure in the upper chamber of the anvil cylinder when the operating valve 48 is moved to exhaust position prior to the initial release of fluid under pressure from the hammer cvlinder.

Automatic means are provided for actuating the sup lemental valve 11 during the dropping of the hammer. In the preferred construction illustrated herein the supplemental valve I! is provided with a vertical valve stem 8| which has secured to it a sprocket 82 which engages a sprocket chain 83 which engages a similar sprocket 8-3 which is fixedly secured to a vertical shaft 85 which is mounted in suitable bearings in the lower portion of one of the columns and in the cylinder supporting beam or yoke. The rod 85 has adjustably secured to it a spiral cam 86 adapted to be engaged by a suitable pin or extenressure from the hammer cylinder and 4 5 sion upon the hammer so that the supplemental valve 11 will be rotated from inlet to exhaust position during the dropping of the hammer and will be reversely rotated bythe hammer during its upward movement. 5

By reason of the construction above described the exhaust valves for the hammer cylinder and for the upper chamber of the anvil cylinder may be manually rotated to any desirable extent to open the exhaust passages from the hammer cylinder and the anvil cylinder. Inasmuch as both the operating valves have been rotated to exhaust position by the upward movement of the hammer the opening of the exhaust valve for the hammer cylinder will permit the hammer to drop. When the hammer is dropped a predetermined distance the cam 86 will be engaged by it and will rotate the supplemental valve 11 to exhaust position, thereby releasing pressure from the upper chamber of the anvil cylinder and permit the air thus released to pass through the relatively larger exhaust valve. By the coordination of the contour and the areas ofthe ports in the exhaust valve for the hammer cylinder and the exhaust valve for the upper chamber of the anvil cylinder above described the movements of the hammer and anvil will be so correlated that the anvil will acquire a momentum equal to that of the dropping hammer while traveling a relatively shorter distance than that traversed by a. the hammer. It will therefore be obvious that the control of both the anvil and hammer is secured by the-simultaneous manually controlled rotative movement of the rod 56 which connects the exhaust valve for the hammer cylinder and II the exhaust valve for the anvil cylinder.

The present invention comprises a novelpedal actuating mechanism for rotating the rod 56 which connects the exhaust valves for the hammer cylinder and the anvil cylinder which will 66 enable the operation of the hammer and anvil to be controlled by either foot thereby leaving both hands of the operator free for manipulation of the work being operated upon. In the preferred construction illustrated a pedal or treadle 8! is I mounted upon the ends of levers 88 which extend through slots in the wall of the front columns 28 and 24 and are connected to a shaft 89 which is journaled in suitable brackets 90 which are mounted upon the base webs of the columns 28 I and 24. One or both of the levers 88 extends beyond the shaft 89 and provided with a suitable counterweight 9|. A rod 92, which is rigidly secured to the lever 88, extends upwardly therefrom and at its upper end is connected by a'ball 63 joint 93 with a substantially horizontal link 84 the opposite end of which is connected by a ball joint 95 to an arm 96 which is fixedly secured to the shaft 56 which connects the exhaust valves. The counterweight 9| normally tends to raise the pedal 81 and actin through the linkage above described to maintain the exhaust valves in closed position. The operator by depressing the pedal 81 to any desired degree may therefore rotate the rod 56 any desired amount and therea by control the volume of air released from the exhaust conduit of the hammer and anvil cylinder so that the speed at which the hammer is permitted to drop and the speed. at which the anvil is projected upwardly will at all times be I. under accurate control. v

While the fluid under pressure may be exhausted directly into' the air, means desirably are provided for conducting the fluid under pressure thus exhausted to a suitable muffler. As-illusll chamber of the anvil cylinder and leads there-- from to a suitable muiiier 99 which may be located in any convenient place, as for example within the recess 9 of the foundation.

- Suitable means are provided for cushioningthe hammer as it approaches the upper limit of its movement of the character disclosed in my prior Patent No. 1,990,478, but modified in accordance with the construction disclosed in the joint application flied in the name of William H. J. Fitzgerald and myself Serial No. 272,584, filed May 9, 1939. This modified construction is graphically illustrated in Fig. 7 of the drawings in which the boss 30 in the cylinder-supporting beam is in the form of a cylinder 99 having a piston I00 provided with a tubular piston rod IOI which is reciprocably mounted upon the piston rod 3| of the hammer-lifting cylinder 21 and extends beyond the lower end of the cylindrical boss 30. The tubular piston IOI is adapted to be engaged by an adjustable collar I02 upon the piston rod so that as the hammer approaches the uppermost limit of its movement the tubular piston rod IOI and piston I00 will be forced upwardly against the pressure of fluid contained in the cylinder 99. Fluid under pressure is supplied from the source through the pipe 99 and a branch pipe I03 to the lower chamber ofv the cylinder 99 and the pipe 99 desirably is provided with a pressure regulating valve I04 in proximity to its connection to the supply pipe 39.

The branch pipe I05, which is provided with an adjustable restricting valve I09, leads from the pipe I04 to the upper chamber of the cylinder 99 above its piston. When therefore the collar I02 engages the lower end of the tubular piston rod IOI during upward movement of the hammer, the piston I00 will be raised thereby further compressing the fluid under pressure in the chamber 99 and forcing it through the pipe I05 and restricting valve I06 back into the pipe I09 which will gradually transmit the pressure to the lower chamber of the cylinder. The compression of the air in the upper chamber of the cylinder 99 will cushion the upward movement of the piston and therefore bring the hammer gradually to rest, while the passage of the air through the closed circuit formed by the pipe I05, the restrict-- ing valve I06, and the pipe I09 will gradually equalize the pressure on opposite sides of the piston I00, thereby permitting the piston and its piston rod to remain in raised position without exerting fluid pressure downwardly upon the hammer. Whenthe hammer is dropped by release of the pressure in the lifting cylinder 2], the weight of the piston I00 and the tubular piston rod IOI will cause them to descend to the normal position shown in Fig. 7.

The relative positions of the connected operating valves, the connected exhaust valves, and the supplemental control valve are graphically illustrated in Figs. 7 to 12 inclusive, in which the upper part of each of the Figures 8 to 12 illustrates the positions of the operating and control valves for the hammer cylinder and the lower part illustrates the corresponding positions of the operating and control valves for the anvil cylinder and of the supplemental valve which is intermediate thereof throughout the cycle of, operations of the hammer.

As illustrated graphically in Fig. 7 the hammer and anvil are at rest, and in engagement with each other with no fluid under pressure turned on from the source of supply. When the hammer is to be put into operation the valves 49 and 45 are opened thereby permitting air under pressure from a suitable source to pass through the pipe 99 and the continuation or branch I9 into the lower chamber of the anvil cylinder and simultaneously to pass through the branch pipe 44, the conduit 20, operating valve- 48 and conduit I9 into the upper chamber of the anvil cylinder; thereby producing such balance of fluid pressure above and below the piston of the anvil cylinder that the weight of the anvil will depress it against the constant fluid pressure in the lower chamber of the cylinder. At the same time the opening of the valve 49 will admit fluid under pressure from the pipe 39 to the pipe 40 and the inlet branch 4i of the conduit 42 which leads to the hammer cylinder, thus causing the piston to which the hammer is attached to be forced upwardly, and the hammer raised.

The connected exhaust valves 52 and 59 are normally maintained in closed position by the action of the counterweight upon the pedal or by a spring or other suitable resilient means. The exhaust branches 41 and 22 of the hammer cylinder and of the anvil cylinder are therefore closed. when the exhaust valve 52 is in the closed position illustrated in Fig. 8, one of its ports 53 is in communication with the inlet conduit 4| and the port 54 at right angles thereto is in communication with the section 41 of the exhaust branch of the conduit 42 and is thus in position to continue the supply of fluid under pressure to the hammer cylinder when the operating valve is rotated to exhaust position.

At the same time the supplemental valve 11, which is located in the exhaust branch 22 of the conduit from the anvil cylinder, is normally maintained in closed position. Air under pressure, which is supplied to the branch pipe 2|, passes through the ports 19 and into the section of the exhaust conduit between the supplemental valve and the operating valve, thereby enabling the supply of fluid under pressure to be continued after the operating valve has been rotated to exhaust position. When the fluid under pressure is thus turned on by the opening of the valves 45 and 49 and fluid under pressure admitted to the anvil cylinders, the hammer will be lifted by the air pressure beneath the piston of the anvil cylinder. As the hammer approaches the upward limit of its movement as determined by the adjustable cam 5| on the rod 49 which connects the operating valves, the operating valves for the hammer cylinder and the anvil cylinder will be rotated to exhaust position, as illustrated in Fig. 8. The hammer will be maintained in lifted position by-the air under pressure which is supplied through the duct and ports I53 and 54 'of the exhaust valve into the conduit 41, thence The hammer and anvil will remain in such separated position so long as fluid under pressure is supplied to their cylinders in the manner above described and until the exhaust valves are rotated aaaopa'z to a position adapted to release fluid under pressure from the respective cylinders.

When the operator desires to drop the hammer he depresses the pedal 81 thereby rotating the rod 56 through the arm and linkage connections shown in Fig. 2 until the exhaust valves reach a desired position in which the escape of fluid under pressure through the ports thereof will permit a desired movement of the hammer and anvil. When the pedal is thus depressed the diametrically opposite ports 53 of the exhaust valve 52 will be caused to communicate with the exhaust branch 41 of the conduit 42 for the hammer cylinder, as illustrated in Fig. 9, thereby permitting fluid under pressure to escape from the hammer cylinder and the hammer to drop. During the initial dropping movement of the hammer the supplemental valve 11 in the exhaust conduit for the anvil cylinder remains closed as also illustrated in Fig. 9. After the hammer has dropped a predetermined distance it engages the cam 86 and rotates it and the actuating rod 85 of the supplemental valve. The sprocket and gear mechanism transmits this rotation to the supplemental valve 11 thereby rotating it to exhaust position as illustrated in Fig. 10. This releases the fluid under pressure from the exhaust conduit of the anvil cylinder and the rate of its release is governed by the exhaust valve 58 in the manner heretofore described. The ports of the hammer exhaust valves 52 and anvil exhaust valves 58 are so coordinated as above described that the release of pressure from the anvil cylinder will project it upwardly while traveling a predetermined distance equal to that of the anvil while dropping a much greater distance. As the hammer approaches the position of impact of the anvil it engages the lower cam 50 upon the rod 49 of the operating valves and rotates them to the positions illustrated in Fig. 11 for supplying fluid under pressure to the hammer cylinder and to the upper chamber of the anvil cylinder thereby enabling the hammer and anvil to be separated immediately after impact without the possibility of a repeated or secondary blow. At this time the supplemental valve remains in exhaust position. However, upon upward movement of the hammer the spiral 86 is again engaged by the hammer and rotates the supplemental valve into the position illustrated in Fig. 12. If the operator holds down the pedal thereby maintaining the exhaust valve in open position the cycle of operation of the hammer will be repeated successively until the pedal is released.

By reason of the construction described herein the manually controlled actuation of the exhaust valves enables the operation of the hammer to be controlled at all times with respect tothe force and frequency of the blow of the hammer. The pedal control of the exhaust valves also enables the operator to use both hands in manipulation of the work. Furthermore the pedal is of suflicient length to enable the operator to control the hammer by the use of either foot thereby enabling the operator to perform the work with less weariness and consequently with greater eficiency.

While the embodiment of the invention has been disclosed with specific-reference to a drop hammer in which compressed air is employed as fluid under pressure, it will be readily understood that any elastic fluid under pressure may be employed and that the term compressed.

air" or its equivalent used in the claims is not a necessary limitation thereof.

It will also be understood that while fluid under pressure is: employed. to project the anvil upwardly with such force that it will acquire a momentum equal to that of the hammer at the moment of impact, other means may be employed for the same purpose.

Furthermore, it will be obvious that both the hammer and anvil may be subjected to similar or diiferent separate forces tending to propel them toward each other and that the hammer and anvil mechanism may be in the form of horizontally movable jaws or platens of a power hammer or press. It therefore follows that the particular embodiment of the invention shown and described herein is of an illlustrative character and is not restrictive of the meaning and scope of the following claims.

Having thus described the invention, what is claimed as new, and desired to be secured by Letters Patent, is:

1. A drop hammer construction comprising a vertically movable hammer, a cooperating vertically movable anvil, means for applying a lifting force to said anvil 'suflicient to impart to said anvil a momentum equal to that of the dropping hammer at the moment of impact,

pneumatically operable means connected respectively to saidhammer and to said anvil operable when supplied with air under pressure to raise said hammer and to depress said anvil against said lifting force, a source of air under pressure, means for supplying said air under pressure to the respective pneumatically operable means, and means including connected simultaneously movable exhaust valves for controlling the release of air under pressure from said pneumatically operable means to cause effective operation of the hammer and anvil.

2. A drop hammer construction comprising a vertically movable hammer, a cooperating vertically movable anvil, means for applying a lifting force to said anvil suiflcient to impart to said anvil a momentum equal to that of the dropping hammer at the moment of impact, pneumatically operable means connected respectively to said hammer and to said anvil operable when supplied with air under pressure to raise said hammer and to depress said anvil against said lifting force, a source of air under pressure, means for supplying said air under pressure to the respective pneumatically operable means, means including connected simultaneously movable exhaust valves having tapering ports regulating the escape of air from the respective pneumatically operable means, thereby to control the movements of said hammer and anvil, and manually operable means for actuating said exhaust valves.

3. A drop hammer construction comprising a vertically movable hammer, a cooperating vertically movable anvil, means for applying a lifting force to said anvil suflicient to impart to said anvil a momentum equal to that of the dropping hammer at the moment of impact, pneumatically operable means connected respectively to said hammer and to said anvil operable when supplied with hair under pressure to raise said hammer and to depress said anvil against said lifting force, a source of air under pressure, means for supplying said air under pressure to the respective pneumatically operable means, and means including exhaust valves fixedly mounted upon a rotatable shaft for simultaneously controlling the release of air under pressure from said respective pneumatically operable means, and treadle mechanism for rotating said position.

4. A drop hammer construction comprising a vertically movable hammer, a cooperating vertically movable anvil, means for applying a lifting force to said anvil suflicient to impart to said anvil a momentum equal to that of the dropping hammer at the moment of impact, pneumatically operable means connected respectively to said hammer and to said anvil operable when supplied with air under pressure to raise said hammer and to depress said anvil against said lifting force, a source of air under pressure, means for supplying said air under pressure to the respective pneumatically operable means, means including exhaust valves fixedly mounted on a rotatable shaft and having similar tapering ports for simultaneously regulating the rate of escape of said air from the respective pneumatically operable means, thereby to control the movements of the hammer and anvil, and treadle mechanism connected to said shaft for rotating said shaft and the exhaust valves thereon to such exhaust position as will cause the hammer and anvil to produce a blow of the desired force,

5. A drop hammer construction comprising a vertically movable hammer, a cooperating vertically movable anvfl, means for applying a constant lifting force to said anvil sumcient to impart to said anvil a momentum equal to that of the dropping hammer at the moment of impact, a source of air under pressure, cylinders having pistons connected respectively to said hammer and to said anvil operable when supplied with fluid under pressure from said source to raise said hammer and to depress'said anvil against said lifting force, means including conduits communicating with the respective cylinders, each having an inlet branch leading to the source of air under pressure and an exhaust branch, simultaneously movable operating valves in said conduits for establishing communication between said source of air under pressure and said cylinders or between said cylinders and said exhaust branches, and connected valves insaid exhaust cally movable anvil, means for applying a lifting force to said anvil sufhcient to impart to said anvil a momentum equal to that of the dropping hammer at the moment of impact, a source of air under pressure, cylinders having pistons connected respectively to said hammer and to said anvil, means for supplying air under pressure to said cylinders to raise said hammer and to depress said anvil against said lifting force including conduits communicating with the respective cylin-. ders, each of said conduits having an inlet branch leading to the source of air under pressure and an exhaust branch leading from said cylinder, simultaneously movable valves in the respective conduits having ports for selectively establishing communication with said inlet branch or with said exhaust branch, means normally positioning said valves to supply fluid under pressure to said cylinders to raise the hammer, means operable when the hammer is raised to a predetermined height to move said valves to exhaust position, connected exhaust valves in the exhaust branches of said conduits normally poshaft and the exhaust valves thereon to exhaust.

sitioned to close the same, means for moving said exhaust valves to open position to permit the hammer to drop, and a supplemental valve in the exhaust branch of the anvil cylinder conduit normally closing said conduit, and mean-s operable when the hammer is dropped a predetermined distance to move said supplemental valve to open position, said exhaust valves being provided with coordinated ports having tapering walls operable to regulate the escape of fluid under pressure from said cylinders and thereby to control the movementsof said hammer and anvil.

7; A drop hammer construction comprising a vertically movable hammer, a cooperating vertically movable anvil, means for applying a constant lifting force to said anvil suflicient to impart to said anvil a momentum equal to that of the dropping hammer at the moment of impact, a source of air under pressure, cylinders having pistons connected respectively to said hammer and to said anvil operable when supplied with fluid under pressure from said source to raise said hammer and to depress said anvil against said lifting force, means including conduits communicating with the respective cylinders, each having an inlet branch leading to the source of air under pressure and an exhaust branch, simultaneously movableoperating valves in said conduits for establishing communication between said source of air under pressure and said cylinders or between said cylinders and said exhaust branches, and connected valves in said exhaust branch conduits manually operable simultaneou-sly to release the air under pressure in said cylinders and to regulate the rate of escape thereof, thereby to control the movements of said hammer and anvil, a supplemental valve in the exhaust branch of the conduit in the anvil cylinder normally closing said branch, and means operable when the hammer is dropped a predetermined distance to move said supplemental valve to open position.

8. A drop hammer construction comprising a vertically movable drop hammer and a cooperating vertically movable anvil, means for applying a lifting force to said anvil suflicient to impart to said anvil a momentum equal to that acquired by the dropping hammer at the time of impact, a pneumatic lifting cylinder having its piston connected to said hammer, a pneumatic cylinder having its piston so connected to said anvil that upon. admission of air under pressure, said anvil will be depressed against said lifting force, conduits communicating respectively with said hammer cylinder and with said anvil cylinder, each having an inlet branch leading from a source of air under pressure and an exhaust branch, simultaneously movable operating valves in said conduits having ports adapted to establish communication between said source of air under pressure and said cylinders, or alternatively, to establish communication between said cylinders and the exhaust branches of said conduits, simultaneously operable coordinated exhaust valves in the respective exhaust branches of said conduits normally positioned to close said" exhaust branches, means operable when said hammer and anvil are moved by admission of air under pressure to said cylinders beyond a predetermined position to move said operating valves to exhaust position, manually operable means for moving said exhaust valves to open position, thereby to release air under pressure from said hammer cylinder and to open the exhaust branch of the anvil cylinder conduit, and a supplementary normally closed control valve in the exhaust branch of the anvil cylinder conduit, and means operable upon-a predetermined dropping movement 0! the hammer to move said control valve to exhaust position and thereby release air under pressure from said anvil cylinder.

9. A power hammer construction comprising a movable hammer and a cooperating movable anvil subject respectively to separate forces tending to proper said hammer and anvil toward each other, cylinders having pistons connected respectively to said hammer and to said anvil, a source of fluid under pressure, means for supplying said fluid under pressure to said cylinders to separate said hammer and anvil, means for releasing said fluid under pressure from said cylinders, to permit actuation of said hammer and said anvil by said forces, including exhaust conduits provided with connected normally closed exhaust valves in vertical axial alinement fixedly mounted on a vertical shaft and having correlated outlet ports of such contour as to regulate the rate of discharge of the fluid under pressure from the respective cylinders, and manually controlled means for rotating said shaft to such exhaust position as will cause the hammer and an vil to produce a blow of a desired force.

10. A power hammer construction comprising a movable hammer and a cooperating movable anvil subject respectively to separate forces tending to propel said hammer and anvil toward each other, cylinders hving pistons connected respectively to said hammer and to said'anvil, a source of fluid under pressure, means for supplying said fluid under pressure to said cylinders to separate said hammer and anvil, means for releasing'said fluid under pressure from said cylinders, to permit actuation of said hammer and said anvil by said forces, including exhaust conduits provided with normally closed exhaust valves having correlated outlet ports with tapering walls of similar contour adapted to regulate the rate of discharge of the fluid under pressure from the respective cylinders, and means for simu taneously operating said valves.

11. A power hammer construction comprising a movable hammer and a cooperating movable anvil subject respectively to separate forces tending to propel said hammer and anvil toward each other, cylinders having pistons connected respectively to said hammer and to said anvil, a source of fluid under pressure, means for supplying said fluid under pressure to said cylinders to separate said hammer and anvil, means for releasing said fluid under pressure from said cylinders, to permit actuation of said hammer and said anvil by said forces, including exhaust conduits provided with normally closed exhaust valves having correlated outlet ports with tapering walls of similar contour adapted to regulate the ratepf discharge of the fluid under pressure from the respective cylinders, means for simultaneously operating said exhaust valves, a supplemental valve in the exhaust port of the anvil cylinder normally closing the same, and means for opening said supplemental valve when the hammer descends a predetermined distance.

12. A drop hammer construction having a vertically movable hammer and a cooperating vertically movable anvil, means for applying a lifting force to said anvil suflicient to impart to said anvil a momentum equal to that of the hammer at the moment of impact, cylinders having pistons connected respectively to the hammer and to the anvil, a source of fluid under pressure,

mental valve in the exhaust branch of the anvil means for supplying said fluid under pressure therefrom to the respective cylinders to raise the hammer and to depress the anvil, exhaust conduits for the respective cylinders, a hollow cylindrical exhaust valve in the exhaust conduit for the hammer cylinder having a port with a taperwail, a hollow cylindrical exhaust valve of greater diameter in the exhaust conduit of the anvil cylinder having a tapering wall of similar contour but presenting a greater area complementary to the greater diameter of the exhaust valve, and means for operating said valves simultaneously to position the ports thereof in the same relation to the exhaust conduit.

'13. 'A drop hammer construction comprising a drop hammer, a lifting cylinder having a piston connected to said hammer, a cooperating vertically movableanvil, a cylinder having a piston connected to said anvil, a source of fluid under pressure, means -for admitting said fluid under 2 pressure to the chamber beneath said piston, a conduit having an inlet branch for admitting fluid under pressure to the chamber of said anvil cylinder above its piston' located vertically below and in substantial parallelism with the inlet 2 branch of the conduit for said hammer cylinder, vertically disposed rotatable operatingvalves in sai dinlet branches connected by a vertical rod having means respectively operable by the dropping hammer to open said valves as the hammer approaches the respective lower and upper limits of its movement, vertically disposed rotatable exhaust valves in the exhaust branches of said conduits connected by a vertical rod and provided with tapering ports, means normally 3 maintaining said exhaust valves in closed position, manually operable means for rotating said exhaust valves to open position to control the movements of the hammer and anvil, a vertical rotatable supplemental valve in the exhaust branch of the anvil cylinder conduit normally positioned to close said exhaust conduit, a vertical actuating rod for said supplemental valve having means operable by the hammer when dropped a predetermined distance to rotate said 4 rod, and means connecting said rod and the stem of said supplemental valve operable by the rotation of said rod to rotate said supplemental valve to open position.

14. A drop hammer construction comprising a drop hammer, a lifting cylinder having a piston connected to said hammer, a cooperating vertically movable anvil. a cylinder having a, piston connected to said anvil, a source of fluid under pressure, means for admitting said fluid under 5 pressure to the chamber beneath said piston, a conduit having an inlet branch for admitting fluid under pressure to the chamber of said anvil cylinder above its piston located vertically below and in substantial parallelism with the inlet branch of the conduit for said hammer cylinder, vertically disposed rotatable operating valves in said inlet branches connected by a vertical rod having means respectively operable by the dropping hammer to open said valves as the hammer approaches the respective lower and upper limits of its movement, vertically disposed rotatable exhaust valves in the exhaust branches of said conduits connected by a vertical rod and provided with tapering ports, means normally maintainin said exhaust valves in closed position, manually operable means for rotating said exhaust valves to open position to control the movements of the hammer and anvil, a vertical rotatable supple cylinder conduit normally positioned to close said exhaust conduit. a vertical actuating rod for said supplemental valve having means operable by the hammer when dropped a predetermined distance, and a sprocket and chain connection between said rod and the stem of said supplemental valve operable by the rotation of said rod to rotate said supplemental valve to open position.

15. A drop hammer construction having a vertically movable hammer and a cooperating vertically movable anvil,- means for applying a lifting force to said anvil sufllcient to impart to said anvil a momentum equal to that of the hammer at the moment of impact, cylinders having pistons connected respectively to the hammer and to the anvil, a source of fluid under pressure, means for supplying said fluid under pressure therefrom to the respective cylinders to raise the hammer and to depress the anvil, exhaust conduits for the respective cylinders, a hollow cylindrical exhaust valve in the exhaust conduit for the hammer cylinder having a port with a tapering wall, a hollow cylindrical exhaust valve of greater diameter in the exhaust conduit of the anvil cylinder having a tapering wall of similar contour but presenting a. greater area complementary to the greater diameter of the exhaust valve, means for op rating said valves simultaneously to position the ports thereof in the same relation to the exhaust conduit, a supplemental valve in the exhaust port of the anvil cylinder normally closing the same, and means for opening said supplemental valve when the hammer descends a predetermined distance.

16. A drop hammer construction having a drop hammer and a cooperating vertically movable anvil, means for applying a lifting force to said anvil sufllcient to impart to said anvil a momentum equal to that of the hammer at the moment of impact, cylinders having pistons connected respectively to the hammer and to the anvil, a source of fluid under pressure, means for supplying said fluid under pressure therefrom to the respective cylinders to raise the hammer and to 5 depress the anvil, exhaust conduits for said cylinexhaust conduits, means normally maintaining said exhaust valves in closed position, means for simultaneously rotating said exhaust valves to ward open position to control the movements of the hammer and anvil, and a normally closed rotatable supplemental valve in the exhaust conduit between the exhaust valve and the umns, a lifting cylinder mounted centrally upon said beam having a piston provided witlfa piston rod iournaled in said beam and secured at its lower end to the hammer, said beam having a buffer cylinder concentric with said pistonrod, a piston in said upper cylinder having a tubular piston rod telescopically mounted upon said beam,

a sleeve upon the piston rod of said hammer adapted to engage the tubular piston rod as the hammer approaches the upper limit of its movement, a conduit having a regulating valve therein provided with branches leading respectively to the upper chamber of said buffer cylinder and to the lower chamber thereof, and a regulatable restricting valve in the branch leading to the upper chamber of the buffer cylinder, said branches forming in effect a closed circuit whereby the upward movement of the piston in the bufler cylinder when actuated by the upward movement of the hammer will compress the fluid in said upper chamber and cause it to flow through the restricting valve into the lower chamber of said cylinder thereby cushioning the upward movement of the hammer until it is arrested and thereafter causing gradual equalization of the pressure upon opposite sides of the piston of the buffer cylinder, thus enabling the piston and piston rod to remain in raised position without exerting fluid pressure downwardly upon the hammer, the weight of the piston and piston rod causing them to descend when engagement of the tubular piston rod by the hammer is released by the dropping of the hammer.

REGINALD P. FITZGERALD.

CERTIFICATE OF CORRECTION.

Patent No. 2,220,057. October 29, 191m.

REGINALD P. FITZGERALD.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 7, second column, line 66, claim 5, for the word "hair" read -ai p 9, first column, line 10, claim 9, for "proper" read --propel--; line 52, claim 10, for "hving" read --having--; and that the said Letters Patent should be read with this'correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 5rd day of December, A.D. 19L;o.

Henry Van Arsdale (Seal) Acting Commissioner of'Patents. 

